DAMPING EVOLUTION DURING PRECIPITATION IN AL-MG-SI ALLOYS

Damping capacity and shear elastic modulus measurements have been carr ied out during precipitation in AlMgSi alloys. After the specimen has been aged at the temperature corresponding to the lowest thermoelectri c power, both damping and elastic modulus increase comparing with the as-quenched state. The effect of strain amplitude was investigated in specimens aged at different temperatures. A critical strain amplitude, epsilon(C), has been observed. For strain amplitudes higher than epsi lon(C), the damping capacity increases strongly with strain amplitude. In addition a relaxation peak appears around 420K after ageing. The s trong damping-amplitude effect and the relaxation peak are attributed to the breakaway of the dislocation from the solute atoms at low tempe rature and to the dragging of these solute atoms by the dislocations a t high temperature respectively.